Tin-tin sulphide (Sn-SnS) electrode has been prepared. Statistical analysis indicates that this electrode is stable and reproducible. It has been found that the electrode can be used in the quantitative determination of S²⁻ in the presence of foreign ions such as F⁻, Cl⁻, Br⁻, I⁻, HCO₃⁻, CO₃²⁻, SO₄²⁻, SO₄²⁻ and NO₃⁻. The potential of the electrode in the presence of S²⁻ has been measured by setting up the following type of cell: Sn-SnS/S²⁻ (saturated) KCl/Hg₂Cl₂, Hg. The electrode shows Nernstian response to pS (−log[S²⁻]) over the range 7·09 to 12·26. The electrode also shows the Nernstian response to pH in the range 7·54 to 11·98 at constant pS. Values ofE⁰, (∂E⁰/∂T)_P and various thermodynamic functions,viz., ΔG⁰, ΔH⁰ and ΔS⁰ for the electrode reaction, Sn_(s)+S²⁻_(aq) ⇌ SnS_(s)+2e, have been determined. Besides, the standard free energy of formation (ΔG_t⁰) and solubility product constant (K_ap) of SnS in aqueous medium at 25±0·1°C have also been determined.